MXPA05014210A

MXPA05014210A - Method and apparatus for providing forward error correction.

Info

Publication number: MXPA05014210A
Application number: MXPA05014210A
Authority: MX
Inventors: Maxim B Belotserkovsky
Original assignee: Thomson Licensing
Priority date: 2003-07-01
Filing date: 2004-06-30
Publication date: 2006-05-31
Also published as: MY134481A; JP2007525089A; US7085282B2; CN1813425A; WO2005006617A3; KR20060025202A; CN1813425B; BRPI0412041A; EP1639724A4; US20050002416A1; EP1639724A2; WO2005006617A2

Abstract

The disclosed embodiments relate to a system for generating forward error correction (FEC) packets. The system includes a first FEC encoder (106) that receives data and encodes first FEC data with the data to form FEC encoded data. Also included in the system is a second FEC encoder (112) that encodes the FEC encoded data to produce second FEC data. An FEC packet formatter (118) formats the second FEC data into an FEC packet.

Description

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METHOD AND APPARATUS FOR RPOLE PROPOSAL CORRECTION OF ERRORS IN ADVANCE Field of the invention The present invention relates to the rate of advance error correction (FEC) in a multi-access time division (TDMA) communication system.

BACKGROUND OF THE I NVE NTION This section intends to introduce the reader to several aspects of the subject that may relate to various aspects of the present invention, which are described and / or claimed below. It is believed that this discussion is useful in proportion to the reader of the background information in order to facilitate a better understanding of the various aspects of the present invention. In accordance with the foregoing, it should be understood that these statements should be read in this respect and not as admissions of the prior art. In a RDMA communication system, a base unit facilitates communication between other base units and multiple local mobile terminals (MTs). The base unit and mobile terminals are typically capable of transmitting and receiving a data signal at a particular frequency or group of frequencies. The data signal is fractured in a number of minor increments known as time shares, which may recur during - 2 - each cycle of the data signal. During a given communication session, a mobile terminal can be assigned a particular time slot. The data of that mobile terminal can be transmitted in the allocated time quota during the duration of a communications session. For a given base station environment, it is typical that some time quotas are not used at any given time. FEC is a technology that is useful in the improvement of digital communications, including TDMA communications. In a communication system employing FEC, the error correction parity bits can be transmitted in conjunction with packets containing real communication data. The error correction parity bits can be used at the receiving end of a data transmission to re-assemble the data accurately. FEC can allow data to be transmitted by using less energy than would otherwise be possible because FEC systems are able to overcome or tolerate some degree of erroneous data. The FEC resistance is typically proportional to the number of FEC parity bits that are transmitted for a given number of data bits. Systems that employ strong FEC codes (for example, by using more parity bits per data bit) are able to tolerate larger numbers of erroneous data bits and still allow the exact reassembly of the data packets. Such systems can provide lower transmitter power, - 3 - higher battery life and increased range of mobile terminals for given information performance. However, transmission scheme parameters (such as the type of modulation, FEC scan, allowed bandwidth, access control to the medium, and the like) for a given communication system have typically been defined and set. In such systems, the only way to increase the range of mobile terminals (or reduce the power consumption for a given range and performance) has traditionally been to increase the transmitting power, which shortens the life of the battery. An apparatus and method that improves the capacity of FEC in TDMA communication systems is desirable.

BRIEF DESCRIPTION OF THE I NVENTION The modalities exposed refer to a system for the generation of packages of correction of errors in advance (FEC). The system includes a first FEC encoder that receives data and encodes first FEC data with the data to form FEC encoded data. Also included in the system is a second FEC encoder that encodes the data encoded by FEC in order to produce second FEC data. An FEC packet formatter formats the second FEC data in an FEC packet.

BRIEF DESCRIPTION OF THE DRAWINGS - 4 - In the drawings: FIG. 1 is a block diagram showing exemplary data and FEC packets according to one embodiment of the present invention; FIG. 2 is a block diagram illustrating an exemplary mechanism for formatting transmission packets according to one embodiment of the present invention; FIG. 3 is a block diagram showing an exemplary mechanism for processing received packets, according to one embodiment of the present invention; and FIG. 4 is a flow diagram of the process, which illustrates the operation of an exemplary embodiment of the present invention.

DETAILED DISCLAIMER OF THE PREFERAL MODALITY One or more specific embodiments of the present invention are described below. In an effort to provide a concise description of these modalities, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such real implementation, as in any engineering or design project, numerous implementation-specific decisions can be made in order to achieve the specific purposes for developers, such as compliance with system-related limits. and related to businesses, which may vary from one implementation to another. In addition, it should be appreciated that such a development effort could be complex and time-consuming, but nonetheless it would be a routine that undergoes design, manufacturing and manufacturing for those of ordinary experience in the field who have the benefit of this exposure. . FIG. 1 is a block diagram showing exemplary data and FEC pak ets according to one embodiment of the present invention. The diagram, which is generally referred to by reference numeral 10, includes a data packet 12 and an FEC data packet 14. As used herein, the expression "data" that remains alone refers to the communication data representing a data signal. The error correction data such as FEC parity bits are referred to as "FEC data". A TDMA communication system may employ such packets as the data packet 12 and the FEC packet 14 to provide communication between a base unit and a multitude of mobile terminals. The data packet 1 2 comprises a first header 16, a data payload 1 8 and a first data bit or bits of FEC 20. The FEC data packet 14 comprises a second header 22 and a second bit or bits FEC 24 data. The header 1 6 may include cue data pointing to the header 22, as shown by the dotted arrow. In accordance with the foregoing, header 16 relates the FEC 24 data to the data packet 12. The embodiments of the present invention may exploit the fact that all TDMA timeslots are not likely to be occupied. (being used) at any given time. This is true due to the improbability that all users associated with a particular TDMA base station are activated at any given time. The unused TD MA time quotas can then be used to transmit additional packets (such as the FEC 14 packet) that contain additional FEC parity bits. Those of ordinary skill in the art will appreciate that, although the exemplary embodiments set forth herein employ the use of TDMA time quotas not used to transmit additional FEC parity data, other methods of parity data distribution may be used. of additional FEC through unused bandwidth. The FEC data 24, which is transported in the FEC packet 14, comprises FEC parity bits for a systematic block code for the currently active mobile terminals. The use of a systematic block code ensures that the original data bits can be recovered without using the additional parity bits, which can be downloaded into the FEC package 14. The FEC 14 package can be generated or used only when there is sufficient bandwidth available (unused time rates) to allow its use. Advantageously, the data payload 1 8 is not changed if the additional FEC packet 14 is used or not. In this way, the average information transfer speed for a given mobile termination remains the same. During periods when the FEC 14 pack is used, the advantages of using a stronger FEC code than would otherwise be available are enjoyed. These advantages may include the ability to decrease the transmitter power in a mobile terminal without changing the average data transfer rate. FI G. 2 is a block diagram illustrating an exemplary mechanism for forming packets for transmission in accordance with one embodiment of the present invention. The block diagram shown in FIG. 2 is generally referred to by reference numeral 100. An information source 102, which may correspond to a source of digitized communication data to be transmitted either from a base unit or a mobile terminal, provides data through a trajectory. signal 104 towards a first FEC encoder 1 06. The FEC encoder 106, which does not need to employ an FEC block code, can be used to provide the FEC 20 data (FIG 1) that is included in the packets data 12 (FI G.1), whether or not additional FEC data 24 is used (FIG 1). The output of the FEC encoder 106, which includes the FEC 20 data (F IG 1) and the associated data payload 18 (FIG 1) is supplied to a payload packet formatter 1 14 through a data path 1 10. The output of the FEC 06 encoder can be referred to as encoded data of-8-FEC. The payload packet formatter 14 may complete the formation of the FEC encoded data in a completed data packet 12 (FIG 1). A header, such as the header of data packs 1 6 (FIG.1), can be created by the formatter of payment payloads 1 14. The header created by the payload packet formatter 1 14 can containing a location flag to leave a mobile terminal receiving the known packet over which the unused TDMA time slot searches for an additional FEC packet, which contains the additional FEC parity data 24 (FIG 1). The completed data packets are supplied by the payload packet formatter 1 14 to a data path 1 20. As an alternative to the use of a header having a flag to a packet of FEC 14 (FIG 1), a base unit can allocate TDMA timeslots in such a way that the reception of mobile terminals can search for FEC packets at pre-defined locations. For example, a payload time quota #i may be associated with a particular FEC fee #k per agreement. In such a case, the receiving mobile terminal may determine whether the associated FEC fee contains an FEC Package by checking the header of that packet to see if the packet contains additional FEC parity data. The FEC encoded packets of the FEC 1 03 encoder can also be supplied to a second packet encoder of FEC 1 12 via a data path 1 08. The FEC packet encoder-1 1 2, which shown in dotted lines to indicate that it can be used only when sufficient extra TDMA time quotas are available, you can calculate additional FEC data 24 (F IG.1) for use in a FEC 14 package (FI G 1) through the use of a systematic FEC block code. The FEC 1 1 2 packet encoder can supply its output, which includes only additional FEC parity data, to a packet formatter of FEC 1 18, also shown in dotted lines, through a data path 1 16. The packet formatter of FEC 1 18 can complete the formation of a FEC packet, in such a way that The FEC 14 packet (FIG.1), by providing a header for the packet and advancing the completed packet through a data path 122. The completed packets of the payload packet formatter 1 14 and FEC packets completed from the FEC packet formatter 1 1 8 can be supplied to a transmitter (not shown) through a data path 124. Although the components for formatting packets shown in FIG. 2 may be employed in either a base unit or a mobile terminal, different considerations may be involved in determining whether additional FEC data will be created and / or transmitted, depending on whether the associated transmitter is in a base unit or a mobile terminal. On the base side, the FEC code generated by - 1 0 - the FEC 1 06 encoder does not have a block code nor does the FEC parity bits have to be located in a contiguous block. When the FEC encoded data from the FEC encoder 106 is encoded by the FEC encoder 12, however, a systematic block code is used. The base unit may desirably have an abundance of available energy for processing circuitry (not radiated power from the antenna for data transmission). An abundance of energy may be much more powerful enough to allow the base unit to create and transmit secondary FEC parity data through FEC 14 packets (FIG.1) inserted in unused time-shares without performance penalty . In such a system, the communication range can potentially be extended to the same average, radiated, allowed energy (or spectral energy density). The same is true for reception and processing of FEC packages. With respect to the transmission of additional FEC parity data by a mobile unit, the mobile units are considered to have limited power, both in terms of power to process additional FEC data and in energy to operate a transmitter. The decision to transmit the FEC 14 packets (FIG.1) for a base unit can always be taken, however, taking into account that the base unit (which is the main TDMA unit) can allocate a time quota empty. This is true because the use of additional FEC protection is generally - 1 1 - more efficient with respect to energy bit per transmitted information. FIG. 3 is a block diagram illustrating an exemplary mechanism for processing received packets according to one embodiment of the present invention. The diagram is generally referred to by the reference number 200. The received packets can be supplied through a data path 202 to a payload packet controller 204 or a packet controller of FEC 206. In parity bits of Additional FECs that are used for a given data transmission, the header of the incoming data packets can be examined by a header decode 21 0 (shown in dashed lines in FIG 3) in order to determine whether the header of the data packets is Incoming data packets 12 (FIG.1) point to an associated FEC data packet 14 (FIG.1). If so, the data may be sent to the receiver (not shown) through a data path 21 2 so that the incoming FEC packets can be routed by the receiver to the FEC 206 packet controller. FEC parity are not used, the data packets can be supplied from the payload packet regulator 204 directly to a FEC decoder 224 through a data path 214. In such case, the data packets are subjected to FEC correction by using only the FEC 20 data that is incorporated in all the data packages. However, if the additional FEC data is used to conserve the life of the battery in a mobile terminal, for example, the data packets of the payload packet controller 204 can be supplied to an FEC 220 decoder via a data path 216 (shown in dashed lines in FIG 3). The FEC packets 14 (FIG.1) of the packet controller of FEC 206 can be supplied in addition to the FEC decoder 220 through a data path 218. The FEC 220 decoder can apply the parity bits of FEC 24 (FIG. 1) to the data payload 18 (FIG 1) and the FEC 20 data (or any combination thereof) contained in the data packets 12 (FIG 1) received from the packet controller 204 payload to produce partially corrected package contents. The contents of package partially. corrected ones can be supplied to the FEC decoder 224, which can apply the FEC 20 data (FIG 1) to the contents of partially corrected packets in order to obtain the payload data decoded by FEC. The payload data decoded by FEC can be supplied from the FEC decoder 224 for further processing via a data path 226. With respect to the decision of a mobile terminal to receive and process additional FEC data, contents in the FEC packets 14 (FIG.1) transmitted by a base unit, a mobile terminal -13 receiver may have two options: (1) stop the decoding of a data packet 12 (FIG.1) until both data packets and the associated FEC packet 14 (FIG.1) are received or (2) ignore the FEC packet and proceed with the reception and decoding in a normal manner. The factors that influence the desire to use additional FEC data by a mobile unit can include if the quality of the input signal is marginal or if an operating range that is beyond what can be achieved is desired. the system with all the TDMA time quotas loaded (that is, when all mobile terminals are online). In the case of marginal signal quality or desired additional range, the use of additional FEC data, such as the data provided by the FEC packets 14 (FIG 1) may be desirable. If the additional FEC data is used by a mobile terminal to extend its range, those of experience in the matter will appreciate that the use of a TDMA time quota available for additional FEC parity data may be lost in each short notice if a An increase in the number of mobile units participating in the data transmission sessions causes the time quota that is being used for FEC parity data to be necessary for the transmission of data packets. FIG. 4 is a process flow diagram illustrating the operation of an exemplary embodiment of the present invention. At - 14 - block 302, the process starts. In block 304, a decision is made as to whether additional FEC data, such as FEC 24 data (FIG 1) from a FEC 14 packet (FIG 1), should be used for data transmission Dadaist. The factors that influence this decision are established in the discussion of FIG. 2 and FI G. 3 above. If no additional FEC data is used, the data packets are processed using only the FEC 20 data (FI G. 1) which is typically included with a data packet 12 (FI G. 1). If additional FEC data is to be used, the additional FEC data is obtained as set in block 306. In block 308, the input data is processed by using the additional FEC data. In block 31 0, the FEC data included in the package is applied to the partially corrected data. In block 31 2, the process ends. Although the invention may be susceptible to various modifications and alternative forms, the specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the invention does not intend to be limited to the particular disclosed forms. Rather, the invention is to cover all modifications, equivalences and alternatives that fall within the spirit and scope of the invention, as defined by the following appended claims.

Claims

- 15 - CLAIMS 1. A system for generating error correction packages in advance, characterized in that it comprises: a first FEC encoder that receives data and encodes first FEC data with the data in order to form FEC encoded data; a second FEC encoder that encodes the FEC encoded data to produce second FEC data; and an FEC packet formatter that formats the second FEC data in a FEC packet. 2. The system for generating FEC packets established according to claim 1, characterized in that the FEC packet is inserted in a timeslot of multiple access by time division (TDMA), otherwise empty. The system for generating FEC packets established according to claim 2, characterized in that a header associated with the data contains information associating the data with the second FEC data contained in the otherwise empty TDMA time slot. 4. The system for generating FEC palettes established according to claim 2, characterized in that a location corresponding to the time quota of TD MA otherwise empty is pre-determined by a TDMA principal. 5. The system for generating FEC packets established according to claim 1, characterized in that - 16 - further comprises: a payload formatter formatter that formats the encoded data of FEC in a data packet. 6. The system for generating FEC packets according to claim 1, characterized in that the second FEC encoder employs a systematic block code to produce the second FEC data. 7. The system for generating FEC packets established according to claim 1, characterized in that the FEC packet is ignored by a receiver in order to conserve energy. 8. A system for decoding an advance error correction pack (FEC), characterized in that it comprises: a first FEC decoder (224) that receives a data packet and an FEC packet and decodes data contained in the packet of data by using the first FEC data contained in the FEC packet in order to produce partially decoded data; and a second FEC decoder (220) that receives the partially decoded data and further decodes the data based on a second FEC data contained in the data packet. 9. The system for decoding the FEC packets established according to claim 8, characterized in that it further comprises: a header decoder for decoding a-1-header associated with the data packet and the identity of the FEC packet. 1. The system for decoding the FEC packets established according to claim 8, characterized in that the FEC packet is received from a predetermined time division multiple access time (TDMA). eleven . The system for decoding the FEC packets established according to claim 10, characterized in that a location corresponding to the TDMA time slot is predetermined by a transmitter. 12. The system for decoding the FEC packs according to claim 8, characterized in that the FEC packet is ignored by a receiver to conserve energy. 13. A method for processing error correction packets in advance, characterized in that it comprises: receiving a data packet containing data and first data from FEC; receive a FEC packet that contains second FEC data; and decide whether the second FEC data is used to process the data. 14. The method set forth in claim 13, characterized in that it comprises processing the data using the second FEC data in order to produce partially-decoded data. 15. The method established according to claim 14, characterized in that it comprises the processing of partially decoded data with first FEC data. 16. The established method according to claim 15, characterized in that the cited acts are carried out in the aforementioned order. 17. The method established according to claim 13, characterized in that it comprises the processing of the data by using only the first FEC data. 18. The method established according to claim 17, characterized in that the cited acts are carried out in the order mentioned. 19. The method set forth in claim 13, characterized in that it comprises ignoring the second FEC data in order to conserve energy. 20. The method established according to claim 13, characterized in that said acts are carried out in the order mentioned.